I have my video files stored on a usb drive attached to a networked XP computer.  I can find files on the computer but not on the usb drive attached to the computer.  I have tries every shared choice I can find but WD HD Live cant find it.  Can any body help ?

Make sure the drive is set to  share files on the network

If you followed the steps to share the folders from your computer you also need to do the same for the external memory.